1. Field of the Invention
The present invention relates to a liquid crystal display panel and a fabricating method thereof, and more particularly to a liquid crystal display panel and a fabricating method thereof that minimize silver dot resistance and prevent common voltage distortion.
2. Discussion of the Related Art
Generally, a liquid crystal display (LCD) device has liquid crystal cells that may be arranged in a matrix. LCDs control light transmittance in accordance with a video signal. Therefore, LCDs display a picture corresponding to the video signal.
Such a liquid crystal display panel may include a thin film transistor substrate and a color filter substrate joined by an adhesive and having liquid crystal material therebetween.
The color filter substrate may include a black matrix for preventing light leakage, a color filter for realizing color, a common electrode for forming an electric field with an opposing pixel electrode and an upper alignment film coated thereon to initially align the liquid crystal molecules.
The thin film transistor substrate may include a gate line and a data line crossing each other on a lower substrate, a thin film transistor (TFT) formed at an intersection thereof, a pixel electrode connected to the thin film transistor and a lower alignment film coated thereon to initially align the liquid crystal molecules.
A liquid crystal display panel of the related art may include an organic protective film formed of a photo acryl and BCB (benzocyclobutene), for example, in order to increase the aperture ratio of a display area. However, a problem arises in that the organic protective film and an adhesive easily separate because of a weak contact force between the organic protective film and the adhesive. To solve this problem, the organic protective film should be formed within the display area excluding a dot area where a silver dot is deposited and a joining area where adhesives are deposited. Accordingly, a common pad may be formed to have a similar structure as shown in the related art of FIG. 1 as it is connected to the silver dot at the dot area and supplies a common voltage to a common electrode provided on an upper substrate.
Referring to related art FIG. 1, a common pad 50 includes a lower pad electrode 51 formed on a lower substrate 41, a pad contact hole 52 passes through an inter layer dielectric 45 to expose the lower pad electrode 51, a middle pad electrode 46 connected through the pad contact hole 52 and to the lower pad electrode 51, and an upper pad electrode 42 directly contacting the middle pad electrode 46.
Accordingly, since the organic protective film is not formed at the dot area, a distance (or “gap”) between common electrodes 32 provided on the upper substrate 1 and an upper pad electrode 42 is large. For example, if a thickness of the organic protective film is about 2.3 μm, a thickness of a spacer is about 4.75 μm and a thickness of a color filter is about 1.7 μm, the space (height) for the dot area becomes approximately 9.0 μm. In such a space, a silver dot 21 should be deposited for electrically connecting the upper pad electrode 42 and the common electrode 32. In such a situation, if the size of silver dot 21 is too small, electrical contact between the silver dot 21 and the upper pad electrode 42 or the common electrode 32 is incomplete. Therefore, electrical resistance at the silver dot 21 is increased, and common voltage signal distortion is generated by such resistance. Inferior picture quality results from the signal distortion. Particularly, in line inversion driving, since a common voltage signal is applied to an alternative signal, a distortion of the common voltage because of resistance upon application of the common voltage to a common electrode is generated. Accordingly, poor picture quality results. Further, it is difficult to vary the size of the silver dot given space limitations of the dot area.